Part 163. The problem of origins. Kinship among living things implies a common origin. We know that kin always resemble one another more or less closely, and this likeness we attribute to their inheriting similar features from the same ancestor. Two individuals which differ from each other no more than do offspring of the same parents, we regard as belonging to the same species; and because of such likeness among the members of a species we feel sure of their having descended from an original ancestor or ancestors which had essentially the same characteristics.

No one doubts that all the kidney-bean plants in the world are the descendants of a plant or plants having the characteristic features of a kidney-bean; but, as we have seen, there are numerous varieties of this species which differ strikingly from one another; often more widely than do many species of the same genus. Why then may not all the species of beans be descended from a more remote ancestor, and so be as truly akin as the members of one species? And if the species of this genus are thus related why not also, though in less degree, the genera of the pulse family, the families of the rose order, the orders of the case-seed class, the classes of the seedwort branch, the branches of the vegetable kingdom, and, indeed, all groups of plants and animals according to their several degrees of resemblance? Why may it not be true that a natural system of classification expresses kinship?

To some readers it may appear profitless to pursue inquiries so remote, and they naturally ask, How can we know or why should we care about the origin of living things? Our answer must be that while of course we cannot know about this absolutely, we may be more or less sure that our conclu

sions are right, and in so far as we really desire to understand the world about us with a view to living in it as best we may, we cannot help wishing to have our beliefs regarding origins harmonize with what we do know. So far as they are in accord with facts, such beliefs help us to put our facts in order so that we may use them to best advantage in living and thinking. Our supreme test of the value and truth of any such belief is the extent to which it enables us to fit fact with fact, and leads us to new facts of importance. Our method must be to apply this test to those beliefs which have been most widely held about the origin of living things. We may be sure that every such belief expresses important truths because of the many facts it must explain in order to be widely accepted. It is, of course, our business to seek truths of importance wherever they may be found, and to adopt the most promising belief until a plainly more truthful view is presented.